1. Field of the Invention
The present invention relates to a copper wire in a semiconductor device, and more particularly, to a copper wire in a semiconductor device in which a barrier layer is formed for improving adhesion of a copper wire without an additional fabricating step; a method for fabricating the same, and a flat panel display device including the same.
2. Discussion of the Related Art
According to development of an information oriented society, fast development of semiconductor devices is progressing for fast storage of large amounts of information. It is a trend that the semiconductor devices are integrated to high device packing densities for storing a large amount of information in a small area.
The semiconductor device is used for driving a flat panel display device which, displays an image, as a general integrated circuit for supplying a signal to the flat panel display device, or as a device for driving a matrix of pixels on the flat panel display device which displays the image directly.
The semiconductor device used in a variety of fields is required to have a reduced area of wire for occupying less area and making fast processing of a large quantity of information. The reduced area of wire and consequential reduction of distance between adjacent patterns, increases a resistance of the wire to cause signal delay and a problem of electron migration in the wire.
In order to solve the above problems, development of a device having a wire of a low resistance is required, and copper Cu which, has a high electric conductivity and a low dielectric constant, is a wire material of low resistance.
However, the copper used as a low resistance wire has a property in which adhesion to a silicon oxide film, silicon nitride film, or glass which is mostly used as an insulating film is poor. Moreover, since the copper has a diffusion coefficient in silicon around 100 times greater than aluminum, a conductive barrier layer is required additionally for improving adhesion to the insulating film and preventing the copper from diffusion.
Though the barrier layer has been formed of material having Ti, TiN, or TaN in the related art, since the material includes metal(s) different from copper, it is required that a fabrication process of the material is performed in a chamber separate from the chamber for depositing the copper. That is, a process for forming the barrier layer becomes complicated.
In order to solve the above problems, a barrier layer of copper nitride is suggested.
Preparation of a Material with an Exact Composition of Copper Nitride, however, is difficult because copper and nitride have poor solubility to each other, Cu3N is a copper nitride suitable enough to be used as the barrier layer.
FIG. 1 illustrates a section of a copper conductive layer 20 of a copper wire formed on a barrier layer 10 of Cu3N on a substrate 1.
Since Cu3N has comparably stable properties, the Cu3N is used for a storage medium of an optical disk. However, since the Cu3N also has a low thermal stability, if heat is applied to Cu3N due to temperature rise of the substrate in a fabrication step after formation of the barrier layer, for example, deposition of copper, Cu in Cu3N is reduced to Cu to form a reduced Cu layer 15 as shown in FIG. 1.
If the Cu3N is reduced to Cu, the barrier layer can not serve as a barrier layer, causing poor adhesion to an underlying film, and failing to prevent the copper from diffusion.